Study On The Characteristics Of Lactobacillus Bulgaricus M-58 In Fermented Milk With Different Fat Content

With the pursuit of healthy diet,low-fat foods are favored by more and more consumers,and milk fat,as one of the main components of fermented milk,plays a key role in the flavor and physical properties of fermented milk.Lactobacillus bulgaricus M-58 is isolated from natural fermented sour yak milk in Mongolia and has good fermentation properties.In this study,Lactobacillus bulgaricus M-58 was inoculated with commercial fermenters as a control,and the fermentation characteristics and storage characteristics were compared and analyzed,and sensory evaluation was performed,combined with liquid chromatography-mass spectrometry to study the effect of Lactobacillus bulgaricus M-58 on the metabolic substances of fermented milk,and the application characteristics of Lactobacillus bulgaricus M-58 in fermented milk with different fat contents were comprehensively evaluated,with the following main results:The addition of Lactobacillus bulgaricus M-58 to fermented milk with different fat content resulted in an earlier gelation point of fermented milk with the same fat content,the TSI values decreased and the viscosity,water holding capacity and texture increased significantly during storage(P < 0.05),indicating that the addition of this bacterium could accelerate the fermentation rate and improve the stability of gel structure during fermentation,as well as improve the textural characteristics and storage stability of fermented milk with different fat contents.Lactobacillus bulgaricus M-58 also showed significant enhancement in sensory quality of low-fat and fat-free fermented milk.A total of 220 differential metabolites were produced by metabolomic analysis comparing with and without the addition of Lactobacillus bulgaricus M-58 in fermented milk with different fat content.The three groups of fermented milk with the addition of Lactobacillus bulgaricus M-58 had relatively high content of small peptides,indicating that this bacterium has a strong protein hydrolysis ability,and the fermented milk without the addition of this bacterium had more substances about glycolysis and TCA cycle enrichment,producing a large amount of organic acids,thus leading to low p H and high titratable acidity during storage.The differential metabolites of Lactobacillus bulgaricus M-58 among all groups in fermented milk with different fat content were enriched in the biosynthesis of secondary metabolites,ABC transporter proteins,and various amino acid metabolic pathways,indicating that the addition of Lactobacillus bulgaricus M-58 to fermented milk with different fat content had an effect on the transport of substances across the membrane and energy metabolism.In summary,Lactobacillus bulgaricus M-58 can improve the quality and sensory properties of whole fat,low-fat,and fat free fermented milk,affecting the metabolites and metabolic pathways of fermented milk.This study can provide theoretical basis and technical support for the development of fermented milk with different fat contents by Lactobacillus bulgaricus M-58.